This invention relates to a process for producing polyamide acid having siloxane bonds and polyimide having siloxane bonds and isoindoloquinazolinedione rings.
In the prior art, as insulating films for electronic parts, typically semiconductors, polyimides having excellent heat resistance and electrical insulating property have been widely applied. Polyimide can be generally obtained by reacting a diamide with a tetracarboxylic dianhydride in an organic solvent to form a polyamide acid which is the precursor of a polyimide, and subjecting this to heating dehydration ring closure. A typical example known in the art is a polyamide acid represented by the following formula (III): ##STR3## obtained from pyromellitic dianhydride and diaminodiphenyl ether, which can be subjected to dehydration ring closure by heating to give a polyimide represented by the formula (IV) shown below: ##STR4## However, the polyamide acid having this structural unit is low in solubility in solvents, and therefore, it is difficult to prepare a solution of low viscosity at high concentration and, even if temporarily be made, there has been involved the problem of markedly poor viscosity stability.
Also, since a high temperature of 300.degree. C. or higher is required when formed into a polyimide by heating, it cannot be used on electronic parts or devices which are sensitive to high temperature treatment.